This invention relates to a method of controlling path audit in a switch. More particularly, the invention relates to a path audit control method of detecting and, and adjusting for, an abnormality in the setting of a path in an ATM switch.
ATM (Asynchronous Transfer Mode) technology has been agreed upon by the ITU-T for the next generation of switching systems and various facilities are carrying out comprehensive research in an effort to realize broadband ISDNs (Integrated Service Digital Networks).
An ATM switch includes (1) a line interface unit for interfacing lines and for executing UPC control, billing control, NDC (Network Data Collection) control and OAM control, etc.; (2) a switch (an ATM switch) for switching cell paths, (3) a multiplexer/demultiplexer for multiplexing cells that have arrived from a plurality of lines, inputting the cells to a switch, demultiplexing cells that have arrived from the switch and outputting the cells to a prescribed line interface unit, and (4) a central controller for controlling the overall switch. The above-mentioned UPC (Usage Parameter Control) includes performing monitoring to determine whether actual cell inflow rate has exceeded a reported cell inflow rate (transmission rate), passing all arriving cells if the reported value has not been exceeded and, if the reported value has been exceeded, discarding cells that are in violation in such a manner that the cell inflow rate will not exceed the reported value.
In such an ATM switch, the central controller (CC) establishes whether control originally to be executed by the line interface unit is possible or impossible [this is referred to as a "CTP (Connection Terminating Point) setting"] and establishes whether UPC control is possible or impossible (this is referred to as a "UPC setting"). More specifically, the central controller performs a CTP setting and a UPC setting for the line interface unit in regard to paths conforming to channel identifiers (VPI/VCI or internal channel identifiers). If both the CTP and UPC settings are performed with regard to a prescribed channel identifier, full control of the line interface unit becomes possible with regard to cells having this channel identifier. In other words, transmission of cells by UPC control, collection of billing data and traffic data and OAM control, etc., become possible. In a case where the CTP setting and not the UPC setting is performed in regard to a prescribed channel identifier transmission of cells having this channel identifier is not possible but operations other than those related to UPC are possible. In a case where neither the CTP setting nor the UPC setting has been performed with regard to a prescribed channel identifier, none of these control operations can be carried out.
Further, the central controller CC sets routing information (tag information) in a multiplexer/demultiplexer in correspondence with channel identifiers. The multiplexer/demultiplexer places the routing information in a table and, whenever a cell arrives, obtains the routing information, which conforms to the particular channel identifier, from the table, attaches the routing information to the cell and then sends the cell to the ATM switch. The ATM switch routes the cell to a prescribed path based upon this routing information.
In the prior art, path matching processing is not executed (1) between the central controller (CC) and multiplexer/demultiplexer (common unit) and (2) between the central controller (CC) and the line interface unit (discrete unit). Consequently, if paths are left unestablished or if paths are left floating for some reason while the central controller CC is executing path setting/release processing in regard to a common unit or discrete unit, the path setting information being managed by the central controller CC and the path setting information being managed by the common/discrete units will not agree. It should be noted that "floating" of a path refers to a situation in which a path that should have been deleted by the central controller CC is left on the side of a common or discrete unit.
Since path matching processing is not executed in the prior art, however, the above-mentioned mismatch cannot be detected and dealt with in a prompt manner. As a result, communication may become impossible. Since a path that should have been eliminated by the central controller CC will be left on the side of a common or discrete unit, a problem such as excessive billing may arise.